An Archi tectural Thesis presented to the Col lege-of Design and Planning, University of Colorado at Denver in partial fulfillment of the requirements for The Degree of Master of Architecture.
David C. Spring 1
The Thesis of David C. Anderson is approved.
University of Colorado at Denver 5 December 1983
TABLE OF CONTENTS
Project Background Hi story
Existing Conditions Architecture
Program Requirements Space Allocations Building Character General Planning Specific Planning
Site Evaluation Soil s
Computer Analysis Cooling Concepts
Every culture develops its own basic design aesthetic. Communications and contact have played a major role in the exchange of design ideas, technologies, and styles. Thus we see the influence of many different eastern cultures throughout much of oriental architecture. Similarly, many western cultures have mingled their styles and aesthetics considerably over the past few centuries. The rapid acceleration of communications technology and the increased contact experienced around the world toward the end of the 19th and the beginning of the 20th centuries has magnified this exchange. The introduction of the Modern Movement in Architecture brought an opportunity to circumvent those cultural differences through what has become known as the International Style. The International Style gave architects a "language" that could be used across all of the cultural barriers that had existed before. Since its introduction it has been used anywhere and everywhere without regard for the culture or the heritage of the specific site. It is time to reassess that tendency and once again respect the cultures of our world.
I propose to design a new residence for the United States Ambassador to Ghana. Because much of the contact with ambassadors and, indeed most of an ambassador's business, takes place at his/her residence, the
residence becomes a symbol of that country's presence in a foreign country. In creating such a symbol one should attempt to meld the aesthetics and design philosophies of both cultures as a symbol of that country's willingness to understand and accept the differences of the two cultures.
America's role in world affairs has changed over the last few years. We are no longer able to portray ourselves as the hero with all the solutions out to save the world and recreate it in our image. That image, strong in the 50's and 60's was wholy embodied in the embassies designed for places like New Delhi, London, and Dublin; buildings which made "no less than a ringing declaration of American presence." Each was "an assertion of American values and a showcase of sophisticated building technology."
Although buildings of that era were not exactly "unresponsive" to local conditions, many times they displayed a lack of understanding of those conditions. For instance, the courtyard in the New Delhi embassy, though a characteristic typical of the venacular architecture, fails to work as a cooling, ventilating element for the building as it does for the local architecture.
America needs to seek a more appropriate,
less heroic imagery for its representational buildings. People's attitudes can be as easily influenced by perceptions through architecture as they can by the rhetoric surrounding it. A country's building can express the attitudes and policies of the country it represents and therefore should be created in that spirit.
Within the program that is generated by the cultural criteria there will be a number of other design considerations to be addressed. One of the issues within this program will be the separation of the public versus the private functions of the residence. Both of these functions must be contained within the same program, therefore separation becomes imperative.
Another major parameter that must be taken into consideration is that of climate. The building is to be located in a hot, humid coastal region about 5 degrees north of the equator. This semi-tropical setting will require special attention to the problems of cooling, ventilation, and lighting. A large portion of this program will focus on the special conditions of the climate and how those conditions can be addressed and, perhaps, overcome.
Because of the violence against U.S.embassies in Teheran-, Islamabad, Tripoli and Beirut,
and because of the danger to diplomatic personnel and property at posts around the world shows no signs of abatement, new designs need to be more security-conscious.
William Slayton, former FBO Director, points out that new buildings will have to have "harder entrances" and many will need to be designed with "safehavens" in which "beseiged staff could find safety from an angry but lightly armed mob for a period of 12 hours." The architect must address the problem without designing a fortress. The alligator filled moat is not, perhaps, the most
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Pre-colonial history in Ghana is complex, linked both to migrations from the north and northeast and to changing rulers, as control of the gold and kola routes changed hands. The oldest states in Ghana were in the north and center; the Dagomba and Mamprussi kingdoms (12th and 13th Centuries).
The rise of the Ashanti Empire in the 16th Century was the real beginning of political history in the area. The Ashanti's began to expand their sphere of influence and by the end of the 17th Century their powerful army was one of the most influential forces in the Gulf of Benin. That influence extended from the northern boundary of modern Ghana and as far as the center of Ivory Coast to the west.
European traders frequented the coast as early as the 15th Century and with the establishment of their first trading post at Elmina, the Portuguese turned away gold, ivory and slaves from the trans-Saharan routes and provoked the decline of the Sahelian states. They encountered competition from the Dutch and the Danes and especially from the British, whose trading posts (organized through an system of chartered companies) supplanted those of other countries after the 16th century.
During the entire eighteenth century the Ashanti state was the principal purveyor of slaves to European traders, and it was not until the 19th century that it began to combat the foreign, mainly British, presence. Four separate British expeditions were required to put down the Ashanti resistance.
There was never any real European settlement. The climate was unattracvtive and not suited to European agriculture. The royal government was there, of course, but the British rarely made the Gold Coast their home. The Gulf of Benin had soon acquired the nickname of the "whiteman's graveyard."
The British were tenacious, though, and they made inroads into the lush interior of their new colony. Malaria, the European colonists bane, was finally controlled with the introduction of quinine and the colony began to take on the built appearance of its Motherland.
A rich plantation economy began to develop in the colony at the beginning of the 20th century, and after 1925 Britain made political concessions to ensure some participation in the colony's government for the African elite, enriched by commercial agriculture and trade.
Ghanaians gained internal self-government in
1951 and finally received their independence on March 6, 1957 with Kwame Nkrumah as Prime Minister. They borrowed their name from history (from the ancient, medieval empire of Ghana in the northern savannah area of west Africa) "to promote a moral and adorn a country...to assert that glories of the African past had reappeared in the new dawn of nationalist independence."
Perhaps the most representative tribe of this arbitrarily formed country is the Ashanti tribe remnants of the former great Ashanti Empire. The seat of that traditional government remains in Kumasi and the head of the tribe, the Ashantehene, remains the second most powerful man in the country second only to Ghana's "Head of State."
Ghana has a population of 12 million people with 2/3 of that population concentrated in the south between Kumasi and the coast. Some 30-35% of the population lives in the urban centers with the growth rate reaching 3.5-4% in the cities. Sixty percent of the working population is engaged in agriculture.
Thanks to high world cocoa prices until the I960's a large class of wealthy people was produced. However in the early 60's the price of cocoa fell sharply and the fragility
of an agricultural economy too dependent on one crop became evident.
The effort at diversification since 1966 has emphasized mechanized cultivation of rice, peanuts, cotton, sugar cane and palm nuts on state farms. Much of the technology and seed money for these operations came from the United States or other "have" countries. Still, Ghana can not feed itself and 33% of its imports are food products.
Economically, Ghana is struggling. With inflation rates averaging 150% per year for the last 6-7 years the people are suffering. Black market money runs at about 6-8 times the official rate. Gas and almost any other imported supplies are short because there is no foreign currency available to purchase imports. The government has a difficult time securing loans to keep from going bankrupt. Right now the country is in debt to the tune of billions of dollars to the IMF.
Politically, Ghana is experiencing some rather turbulent times. There have been several coups in the past decade and many more attempted coups. Presently the government is in the hands of the military. In the past there have been numerous governments that have shown a decided alliance with the West but this present power has been displaying strong sympathies toward the Soviets.
This is a disturbing turn of events as far as the security and general ease of State Department employees are concerned. Before 1978, there was never any question about the security of our "mission" in Ghana but recently the embassy office building was vacated on the grounds that it was "indefensible."
The U.S. relationship with Ghana is presently focussed on the administration of hefty amounts of foreign aid most in the form of agricultural development projects. Of the 200-300 Agency for International Development (AID) employees in Ghana at this time more than 90% are stationed in Accra. Only a handful of field personnel actually oversee the distribution of aid money and technology in the interior. The actual embassy staff has less than 50 employees right now. There are also 150 Peace Corps Volunteers in country with a support staff of 10 people (mostly Ghanaians) in Accra.
The office of Foreign Buildings Operations in the State Department administers and oversees all of the Governmenmt's construction overseas. The FB0 is advised on all matters of architect selection and design by a three-member panel of architects that reviews projects at regular intervals through out the
Building overseas provides different and frustrating challenges for the architects. This is particularly true in the third world countries where materials suppliers can be unreliable, technology can be at least a generation behind Western standards, bonding procedures may be practically non-existent, inflation rates may flucuate wildly, and conventional contract language is all but meaningless. When coupled with language barriers, differences in local customs, currency restrictions, and FBO's special requirements, designing for the State Department might become rather frustrating.
Projects with the FB0 are especially vulnerable to the currents, cross-currents and under-currents of international politics. "The sudden emergence of a generalissimo or an ayatollah in a far-off land can deflect U.S. foreign policy abruptly and stall or even collapse an FB0 project without warning at any stage of its development."
Describing an indigenous architecture for Ghana is a bit presumptuous. We have a limited knowledge of anything more than the mud huts that are so common throughout the west coast of Africa and defining any
specific characteristics of those would be of limited use for this project. We know that the Ashantes had a very distinctive construction technique that involved heavy mud walls surrounding a wooden roof support system. The roof was then made of a heavy mud slab supported only by the poles and not connected to the walls. Unique but hardly worth pursuing as a prototype.
In the northern areas of the country, on the other hand, we see an extensive use of the very inward facing compounds known as "kraals." These are common throughout the Sahel region of Africa and deal more with the social institution of the family and the need to defend against animal life than do the simple mud huts of the Ashantes. Perhaps, the kraals are the first real inkling we get of an architecture that could have been indigenous had it been allowed to evolve.
Ghanaian architectural evolution got a kick in the pants when the Europeans arrived. They brought with them a premade architectural heritage. It was technically far more advanced than the indigenous stuff and from then on, no Ghanaian worth his weight in cocoa beans could build anything else. The Euro-pean influence over the next three centuries managed to completely replace the heritage that had existed before that the only remaining evidence of "indigenous"
architecture is that which can still be found deep in the jungle where materials and technology do not mean as much as they do elsewhere .
Today, the architecture that one sees throughout the southern part of the country is almost exclusively colonial in style. The new style and materials have been adapted in some cases to maintain the flavor of the older uses but the architecture remains very British. The only place where one gets away from that is in the north where one can still find the kraals and the mud mosques.
Peter Winklestein of Marquis and Associates said that finding an architecture to relate to in designing the new embassy in Costa Rica was virtually impossible. They decided not to try to imitate the architecture, both because it would be difficult to pin down a style or type but also because it might insult the locals. They chose instead to borrow some of the planning and layout ideas and then introduce their own vocabulary.
In recent decades the tendency in Ghana has been toward International Style houses. There has also been an extensive use of the International Style in the design of office, government and dormitory buildings throughout the country. Much of this is due to the relative simplicity of the style and the ease
of construction. The availabilty of concrete and the extensive familiarity with its use also plays a role in the choice of style.
One characteristic of all of the chiefs houses (palaces) that I visited was the existence of a parade ground or large semi-enclosed courtyard for holding ceremonial gatherings or festivals. The position of the chief is similar to that of the ambassador in that he is a very public figure. The chiefs always seemed to need to retreat back into their home to become human again after being a demi-god in their courtyard all day.
The following net areas are recommended by the Foreign Buildings Operations Office of the State Department and are based on the typical Embassy Residence requirements for a class II post. All of the areas are given in square meters (with imperial areas in parentheses).
1. Entrance Foyer 19 (200)
2. Cloak Room 11 (120)
3. Women's Powder Room 11 (120)
Women's Lavatory 6 (60)
Men's Lavatory 7.5 (80)
4. Reception Room 56 (600)
5. Salon 56 (600)
6. State Dining Room 56 (600)
7. Library-Study 28 (300)
8. Parlor 19 (200)
9. Stair Hall 25 (260)
SubTotal 294.5 (3,140)
1. Family Living 28 (300)
2. Family Dining 23 (240)
3. Bedrooms and Baths:
Master Bedroom 28 (300)
Dressing Room 7.5 (80)
Bath #1 (private) 7 (70)
Bedroom #2 25 (270)
Bath #2 (private) 6 (60)
Bedroom #3 20.5 (220)
Bedroom #4 19 (200)
Bath #3 4 (40)
4. Family Pantry 4 (40)
SubTotal 172 (1.820)
1. Bedroom #1 25 (270)
Bath (private) 6 (60)
2. Bedroom #2 20.5 (220)
Bath (private) 4 (40)
SubTotal 55.5 (590)
1. Kitchen 33 (350)
2. Food Storage 24 (250)
3. Butler's Pantry 19 (200)
4. Butler's Office 5 (50)
5. Central Linen Storage 9 (100)
6. Laundry 9 (100)
7. Flower Room 5 (50)
8. Refrigerators &
Freezers 3 (30)
9. Cool Storage (Wine) 14 (150)
10. Sewing and Service 14 (150)
11. Servants' Dining 9 (100)
12. Servants' Bedrooms 48 500
(4 0 6m2)
13. Servants' Bath 8 (80)
(2 @ 4m2)
14. Servants' Lavatory 3 (30)
15. Servants' Sitting Room 11 (120)
16. Garage (2 0 24) 48 (500)
17. General Storage 28 (300)
18. Garden Storage 7.5 (80)
19. Trunk Storage 9 (100)
20. Trash Storage 5 (50)
21. Mechanical 24 (250)
SubTotal 335.5 (3,540)
Total Net 857.5 (8,990)
For purposes of estimating and controlling residence costs the FBO has established a 75% efficiency factor. Thus:
Gross Area = 1142.5m2 (12,150)
Additional storage space has been added to the State Department figures due to the nature of the country and the necessity to stockpile many food and clothing items that may become unavailable locally.
The character of the building should express its representational nature as well as its residential function. It should express the rpresentative nature of the building in terms understood by, and compatible to, the Ghanaians. The emphasis should be on quality but without ostentation or luxury. Above all there should be a deference to Ghanaian architectural traditions and materials.
There should be a clear separation of public and private functions; the State Department policy is to place all of the private functions in the second story and above. There needs to be an easy "flow-through" circulation through the representational spaces.
Exterior entertainment facilities must be provided directly adjacent to the representational functions of the residence:
3. A Covered "Patio"
Guest parking should also be provided since there is little or no parking available on the street.
There are several requirements that are site specific that must be taken into
consideration including adequate water storage and backup electrical and sewage disposal systems.
Special climatic considerations include dust control (for Harmattan), insect control (for mosquitos), sun shading, ventilation. For more information on clamatic control, see the section on "Climate."
Security can be addressed in a number of ways of which gatehouses, walls, and/or fences are the suggested responses. Presently, the trend is toward fortresses but there should be a way to avoid that. The FBO suggested that there should be no windows on the first floor and ground cover kept to a minimum.
A covered main entry for access undercover from vehicles to the residence is essential, a solution might suggest itself in the form of a porte cochere.
All bedrooms except servants bedrooms, shall have a minimum dimension of 3.6m (121).
Each person occupying a bedroom shall be provided with a minimum of six linear feet of closet space.
Various assumptions will have to be made for this project. The first assumption that will be made is that the site for the existing residence will be the site for this project.
The site is located in the capital city of Accra, on the coast of the Gulf of Benin on the Atlantic Ocean. The residence is within two kilometers of the center of Accra and one kilometer from the American Embassy. The immediate vicinity is an old residential section of the city. Many of the residences in the area are old colonial estates built around the beginning of the 20th Century. There are also several large International Style houses and a few Mediterranean villas.
The site is located on Independence Avenue, a major arterial of the city (although it is only a two lane road). The site is a nearly rectangular piece of land approximately 120 meters by 75 meters and encompasses an area of about 0.9 hectares. The long axis runs ^southwest-northeast parallel to Independence Avenue and can only be accessed along the avenue.
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An open gutter runs along both sides of the road and there is a two meter setback between the roads and the private properties. This setback is unpaved but acts as a sidewalk. Traffic on the "sidewalk" is light during the day and non-existent at night.
There is a very slight slope (1% maximum) from east to west. The site is presently planted with grass and decorative shrubs, plants and trees.
Services to the site are from a service alley (8 meters wide) that runs parallel to Independence along the back property line. Services to the site include electricity, telephone, water and sewage, but do not include gas.
Gas tanks are typically stored on site if they are needed. A 20 cubic meter water storage tank should be included on site in lieu of water shortages. Electricity runs at 220-240 volts: transformers needed to be included if American utensils are to be used.
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DEPTH DESCRUTI OH' . SAMPLE
FRCM M. fiT0 M. DEPTH TYPE
0 0.610 Deep brown, medium to mainly 0.152 D
fine sand with little silt.
0.610 1.524 Brown sandy clay with some 0.914
vague reddish-brown patches to SS
1 add spots. 1.524
1.524 1^81- Reddish-brown to .yellowish- 1.524
' / 1 brawn medium to fine stiff to U44
I sandy clay. 1.981
1.981 Â£.667- Reddish brown and grey 2.057
sandy clay with some weathered to SS
medium grained quartz gravel. 2.667
2.667 3.810 Angular boulders and cobbles 5.591 V
of quartz cemented by brown 3.200 D
; grey stiff sandy clay, 3.200
Soils information was taken from a site investigation report for a site approximately 1 kilometer from the site in question. The report is acceptable since the soils in the region are relatively homogenous.
The results of the testing (11 auger bore holes) showed that the soils had an allowable bearing capacity of 2.4 kg/cm32 (approx. 4000 psf). There is an expected settlement of 4.5 cm which is not considered excessive as most of the settlement would take place during construction. The settlement would be due in part to the sandy nature of some of the 1ayers of soil.
Care will have to be taken in determining the materials of the building and the sizing of footings to avoid heavage. Swell pressures of up to 1 kg/cm32 were observed during consolidation tests. Good drainage should be provided around any buildings.
The State Department policy on building materials is that "after the first 90 days of construction everything has to be imported from the states." It is a blanket policy that may well affect the design of the building. The architect must assume a certain construction time table that would respect that time constraint. With labor and construction techniques overseas that requires some adjustment to whatever assumptions can be made stateside. Most of the structure and even some of the interior trim can be completed in that time. In the case of a residence, this restriction is not as critical as it could be in the case of a larger, more time consuming project. One way to get around that restriction is through phasing, as in the case of more than one building on the same site.
Ghana is a country of severe materials shortages. Imported goods are difficult if not impossible to acquire on the open market. The shortages have also made the costs of those materials prohibitive. Indigenous materials on the other hand are abundant and should be used wherever possible.
Ghana is a country rich in hardwoods and wood craftsmen. Wood carvings have played a major role in the history and culture of the land.
In addition, the British brought with them a tradition of wood and stone craftsmanship and established a network of vocational training that has contributed heavily to the development of the indigenous building industry. Mahogany, "odum," and "sisiwa" are the most readily availabe and it is not uncommon to find roofs framed out of these woods.
When working with wood in the tropics and the semi-tropics it is necessary to provide adequate ventilation to prevent mildew and rot. Wood is not recommended for use below or near grade because of the prevalence of termites or "white ants." Metal termite shields need to be considered whenever wood is used within 800mm of the ground.
An interesting side effect of Ghana's materials shortages is that it has created a dependence upon craftsmanship. Joinery has remained a major craft if only because nails and reliable glue are not readily available. Nailless joints are the pride of carpenters everywhere and in Ghana they are a trademark.
Concrete plays a major role in the Ghanaian building industry. It would make sense to utilize that technology in this project since that would provide the proper ratings for fire-resistance and security would be more easily incorporated in to the design than if
one were to use wood or some other, less massive material.
Steel of consistent quality and strength is not readily available and would have to be imported. This is in opposition to the policies of the State Department. Therefore the use of steel should be restricted as much as possible in the design of the building.
Most, if not all, roofing materials (aside from the traditional thatching) need to be imported. Although Ghana has one of the largest aluminun production plants in the world, aluminum is not readily available in the country in a usable form. The aluminum is shipped out of country in the form of ingots to factories elsewhere where it is then formed into sheets or pipes or whatever shapes are needed. Since it would then have to be imported back into the country, aluminum is no more readily available than any other imported material.
Ghana's climate is mainly the result of the interplay between two principal airstreams: the hot, dry, tropical, continental airmass or "harmattan" from the northeast and the moist, relatively cool, maritime airmass or monsoon from the southwest across the Atlantic. The "Inter-Tropical Convergence Zone," along which these two airmasses meet, oscillates north and south in accordance with the movements of the overhead sun and is one of the main determinants of the incidence of rainfall in the region.
In the southern part of the country there are two rainy seasons: April to July and September to November. Accra is subject to this same climatic rhythm, but, is much drier (750-800 mm of rainfall) than further west (1300-2100 mm). This is due to the fact that the coast here is oriented parallel to the maritime monsoon winds from the southwest. This also allows the temperature swings to be more extreme.
These temperatures, coupled with equally high relative humidities, which drop significantly only during the harmattan, tend to produce oppressive conditions. This is relieved only by the relative drop in temperature at night and the local incidence of land and sea breezes near the coast.
The following analysis was generated from D. Woolard's "Climat" program with data collected from NOAA and ASHRAE. The program essentially follows the "Mahoney Table" format as set out by Koenigsberger (1973, pg. 237-246). This method was originally devised for tropical climates and gives an accurate analysis for this site.
TABLE 1. CLIMAT IC DATA < DEG C >
MON n-l MAX MIN RANGE
JAN 32.7 1.9. A 13.3
FEB 32.7 2 :i.. 1 11. A
MAR 32.7 21 A 11 1
APR 32.7 21.6 11 1
MAY 32.7 21 A 11.1
JUN 31.A 21.. 1 10.. 5
JUL 29 A 20.5 8.8
AUG 28.3 20 8.3
SEP 29.. A 21.1 8.3
OCT 31 .1 21 1 10
NOV 31.6 21.6 10
DEC 32.2 20.5 11.6
HIGH - 32.7 LOU = 19. A
AMT 26.. 1. AMR ~ 13.3
TABLE 2 01. . t: m a t i: C DATA ( RH P ft E c :i: p ;,j j. N T.i >
MON T i l MAX m :i: n AVE G*RAIN UP US
JAN 95 6 :i 78 4 16 UNO ssu
F E B 96 6 1. 78.. 5 4 37 SSU UNU
M A ft 95 63 79 4 73 SSL) u
APR 96 65 80-5 4 82 SSU U N u
M A Y 96 6 8 82 4 145 ssu UNU
JI...IN 9 7 7 4 3 5.. 4 193 SSU U N LI
JUI 9 7 / 86.. 5 4 49 ;> L.l ;u
aijg 9 / 7 7 :> 7 4 16 B UJ W > 1*)
SEP 96 7'? 8 4 4 40 S 8 UJ su
ET o c i 9 7 71. 84 4 80 ssu UNU
NOV 97 7) A) 81. 5 4 38 UNU SSU
DEC 9 7 6 4 80.. 5 4 18 U N U ssu
Comfort Limits: Day 22-27 C.
Night 17-22 C.
* Humidity Group: #4, above 70%
This very hot and humid climate demands some alternative considerations to the design and orientation of any structure that is built there. The major factor that has to be taken into consideration is the combination of oppressive heat coupled with excessive humidity. The humidity has the effect of making the heat even worse than it would be in a dry climate. There is a considerable shift in man's comfort zone as one increases the moisture content of the air.
There are four alternatives to be reviewed with different alternative solutions for each.
a. Reduce the amount of heat absorbed into the building.
b. Reduce the amount of humidity in the building.
c. Extract heat from the building.
d. Extract humidity from the building.
Three basic alternatives are available before one has to go to the technology of mechanical or electrical air-conditioning; radiant, evaporative, and/or conduction cooling.
Radiant cooling is probably not a major factor in Ghana's climate because of the high humidity. The problem is getting the sky temperature to drop significantly below the
ambient temperature of the air. Cloud cover severely reduces the sky cooling rate and a heavy overcast can effectively shut off any radiant cooling effect.
Another deterant is breezes. The constant movement of the air will reduce heat loss to the sky by as much as 85% in a 10 kph wind. Watson (1983) concludes that "radiaton cooling is generally not suited to warm, humid climates in which night time breezes prevail."
Another form of cooling would be the concept of evaporative cooling. Two very different approaches can be taken: (1) roof sprays and ponding can dissipate solar heat absorbed at the surface; (2) evaporative treatments can be used to extract heat from the interior. The extraction treatment requires a close coupling between the interior space to be cooled and the evaporating surface (ie. a roof pond with a highly conductive roof structure).
Wet-bulb depressions are the best indicators of the effective potential for evaporative cooling. For this reason, once again, this method is perhaps best suited to dry climates. This might explain the high incidence of swamp cooling techniques in the arid southwest United States. Ghana's wet-bulb depression is low, with a 5-10 C. range.
The value of this type of heat dissipation relies heavily on various design mechanisms for resisting heat gain. Three basic concepts should be considered:
1) Maximize the solar reflectivity of the roof surface.
2) Ventilate the underside of the roof.
3) Insulate to resist the conductive intrusion of solar heat.
One note to these concepts is that ventilated roof effectiveness is best measured by dry-bulb. This is also the case with highly reflective and shaded roofs. Wei 1-insulated and well-shaded roofs receive little additional benefit from evaporative cooling. With poorly insulated roofs, roof-sprays can be very effective in hot, humid climates where solar loads are high but winter heat gains are negligible.
A roof pond would be a desirable solution to the problem of extracting heat from the interior. Since it is neither necessary nor desirable for the "wet roof" to be exposed to the sky, the evaporative surface could be shaded. Such shading devices could also serve to direct natural breezes over the "wet roof."
A third process of cooling would be conductive cooling. The only "sink" to which the building can continuously lose heat by
means of conduction is the ground. A problem arises in that the potential for the ground to work as a heat sink is greatly affected by the actual presence of the building. Any device which extracts "coolth" from the ground in turn raises the temperature of the surrounding soil.
A problem that arises when attempting to use the ground as a heat sink is how to situate the structure for maximum ground coupling without losing any ventilation potential. One solution that has been attempted is the use of earth-air exchangers or "earth pipes." These provide a means of exploiting the cooling potential of the ground without actually building underground. Again, the highest potential for this type of cooling occurs in arid climates with large temperature swings.
Evaporative cooling is probably the most effective alternative for this project but the real emphasis will have to be on ventilation and the use of natural convective currents to pull hot air out of the building and create a vacumn into which cooler air can be introduced. Pockets or traps of cool air should be created for that purpose.
The following concepts provide a number of alternative solutions which may be pursued toward those ends.
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VEGETATION AND WATER
1) Use of ground cover and planting to
2) provide on site cooling.
Use of roof spray or roof ponds for
COURTYARDS COVERED PATIOS OR PORCHES
1) Provide outdoor semi-protected areas for temperature moderation.
1) Minimize reflectivity of ground and building surfaces outside windows facing the sun.
2) Use neighboring landforms, structures or vegetation for shading.
3) Shape and orient the building shell to minimize its exposure to the sun.
4) Provide shading for walls exposed to the sun.
5) Use heat-reflective materials on surfaces oriented to the sun.
1) Use landforms, structures or vegetation to increase exposure to breezes.
2) Shape and orient building shell to maximize exposure to breezes.
3) Use "open plan" interior to promote air-f 1 ow.
4) Provide vertical air shafts to promote convective loop.
5) Use double roof and wall construction for ventilation within the building shell.
6) Orient door and window openings to facilitate natural ventilation for prevailing breeezes.
7) Use wing walls, overhangs, and louvers to direct air-flow into interior.
8) Use lovered walls for maximum ventilation control.
9) Use roof monitors for ventilation.
1. Kroenigsberger, O.H., etal., Manual of
Tropical Housing and Building, Langmere Group Limited, London, 1973.
2. Szokolay, S.W., Environmental Science Handbook, John Wiley & Sons, New York, 1980.
3. Watson, D., K. Labs, Climatic Design McGraw-Hill, New York, 1983.
The State Department policy concerning building codes around the world is to take the most stringent codes and apply them to whatever building is being designed. This includes whatever codes are in effect in the country being designed for as well as all American codes. The general experience is that American codes are far more conservative than most third world codes. In many cases there are no codes in the third world countries or the codes that have been established only pertain to commercial buildings or buildings that are over three stories in height.
Ghanaian building codes are unavailable. Therefore, the Universal Building Code (UBC) will serve as the major constraint/influence for building codes for this project. The building is broken down into two separate occupancy types with the public section designated A-3 and the private section designated R-3. Handicapped access is required for the entire building and most be incorporated into the design from the start.
The following excerpts from the UBC are general. If more detailed information is needed one should go directly to the source with special attention to parts V, VI, VII, IX, and X.
REQUIREMENTS BASED ON OCCUPANCY
Chapter 5 Classification of All Buildings By Use or Occupancy and General Requirements For A11 Occupancies.
MIXED OCCUPANCY Sec. 503.
(a) General: When a building is used for
more than one occupancy purpose, each part of the building comprising a
distinct "Occupancy," as described in Chapters 5 through 12, shall be separated from any other occupancy as specified in Sec. 503(d).
When a building houses more that one occupancy, each portion of the building shall conform to the requirements for the occupancy housed therein. The area of the building shall be such that the sum of the ratios of the actual area divided by the allowable area for such a separate occupancy shall not exceed one.
(b) Forms of Occupancy Separations: Occupancy separations shall be vertical or horizontal or both or, when necessary, of such other form as may be required to afford a complete separation between the various occupancy divisions in the building.
Where the occupancy separation is horizontal, structural members
supporting the separation shall be protected by equivalent fire-resistive construction.
(c)Types of Occupancy Separations:
4. A "one-hour fire-resistive occupancy separation" shall be of not less than one-hour fire-resistive construction. All openings in such a separation shall be protected by a fire assembly having a one-hour fire-protection rating.
LOCATION ON PROPERTY
(a) General: Buildings shall adjoin or have access to a public space, yard or street on not less than one side. Required yards shall be permanently maintained.
For the purpose of this section, the centerline of an adjoining street or alley shall be considered an adjacent property line.
Eaves over required windows shall be not less than 30 inches (760mm) from the side and rear property lines.
(b) Fire-Resistance of Walls: Pro-
jections beyond the exterior wall shall not extend beyond:
1. A point one-third the distance to the property line from an exterior wall; or
2. A point one-third the distance from an assumed vertical plane located where fire-resistive protection of openings is first required due to location on property, whichever is the least restrictive. When the openings in exterior walls are required to be protected due to distance from the property line, the sum of the area of such openings shall not exceed 50% of the total area of the wall in each story.
(c)Buildings on Same Property and Buildings Containing Courts: For the purpose of determining the required wall and opening protection, buildings on the same property and court walls of buildings over one story in height shall be assumed to have a property line between them.
EXCEPTION: In court walls where opening protection is required such protection may be omitted, provided (1) not more than two levels open into the court, (2) the aggregate area of the building including the court is within the allowable area.
ALLOWABLE FLOOR AREAS Sec.505.
For Occupancy type A-3 the allowable
floor area with type I construction is unlimited. For type II fire-resistance construction the allowable floor area is 29,900 square feet (2800 square meters).
For occupancy type R-3 the allowable
floor area for any type of construction is unlimited.
MAXIMUM HEIGHT OF BUILDINGS AND INCREASES Sec. 507.
For occupancy type A-3 the maximum
allowable height is unlimited with type
I construction and 12 stories with type
For occupancy type R-3 the maximum
allowable height is unlimited with type
I construction and 3 stories with type
FIRE-RESISTIVE SUBSTITUTION Sec. 508.
Where one-hour fire-resistive
construction throughout is required by this code, an approved automatic sprinkler system, as specified in
Chapter 38, may be substituted, provided such a system is not otherwise required throughout the building.
EXCEPTION: Such substitutions shall not waive or reduce required fire-resistive construction for:
1. Occupancy seperations.
2. Exterior wall protection due to proximity of property lines.
3. Area separations.
4. Shaft enclosures.
6. Exit passageways.
7. Type of construction separation.
8. Atriums constructed in accordance with Sec. 1715.
Water Closet Room Seperation: A room in which a water closet is located shall be seperated from food preparation or storage rooms by a tight fitting door.
(a) Facilities shall conform to all requirements of Barrier Free Design Standards as set forward by the American Institute of Architects and the UBC 82 as defined in sec. 511 (a)
Chapter 6 - Requirements for Group A
GROUP A OCCUPANCIES DEFINED Sec. 601.
Group A occupancies shall be:
Any building or portion of a building having an assembly room with an
occupancy load of less than 300 without a stage, including such buildings used for educational purposes and not classed as a Group E or Group B, Division 2 Occupancy.
CONSTRUCTION, HEIGHT AND ALLOWABLE AREA Sec. 602
(b) Special Provisions: Division 3 Occupancies located in the basement or above the first floor shall be of not less than one-hour fire-resistive construction.
Chapter 12 - Requirements for Group R
GROUP R OCCUPANCIES DEFINED Sec. 1201.
Division 3. Dwellings and Lodging
EXIT FACILITIES Sec. 1204.
Every sleeping room below the fourth story shall have at least one operable window or exterior door approved for emergency escape or rescue. The units shall be operable from the inside to provide full clear opening from the inside without the use of seperate tools.
All escape and rescue windows from sleeping rooms shall have a net clear opening of .57 square meters. The minimum net clear opening height
dimension shall be 630mm. The minimunnet
clear opening width shall be 525mm. Where windows are provided as a means of escape or rescue they shall have a finished sill height of not more than 1155mm above the floor.
Bars, grills, grates, or similar devices
may be installed on emergency escape or rescue windows or doors, provided such devices are equipped with approved release mechanisms which are operable from the inside without the use of a special key or special knowledge or effort.
Note: The preceding code search is by no means exhaustive. It is not intended to be. The purpose is to get the designer familiar with the restrictions and parameters that will be faced during the design process. Two areas of further concern should be the
Handicap Access and the Exit requirements as set out in Chapter 33 of the 1982 UBC.
1. Alexander, C., A Pattern Language,
Oxford University Press, New York, 1977.
2. Boateng, E.A., "Ghana, Physical and
Social Geography," Africa South of the Sahara, Europa Publications, LTD,
3. Drummond, H., Tropical Africa, Hoader and Stoughton, London, 1988.
4. Fitch, James M., Historical Preservation, Mcgraw-Hill, New York, 1982.
5. Fry, E., Tropical Architecture for the Dry and Humid Zones, R.E.Krieger Publishing Co., Huntington, New York, 1974.
6. Gordon, B.F., "America Turns a Fresh Face Overseas," Architectural Record, McGraw-Hill, New York, Dec. 82, pg. 96-113.
7. Lederer, W.J., Burdick, E., The Ugly American, W.W.Norton and Co., New York, 1958.
8. Moore, C., The Place of Houses,
9. Olgyaye, V., Design With Climate, Princeton University Press, Princeton, N.J., 1963.
10. Ramsey, P.G., "Towards a Tropical
Architecture," Architectural Digest,
April, 1959, pg. 128-138.
11. Rapaport, A., House, Form and Culture,
Prentice-Hall, Englewood 1969. Cl iffs, N.J.,
12. Remy, M., Ghana Today, Holland, 1977. Editions, J.A.,
13. Sieber, R., African Furni ture and
Household Objects, Indiana University Press, Bloomington and London, 1980.
ee also Climate bibliography.
Heilman, Rex; Project Architect, Foreign Buildings Operations, State Department; Washington, DC; 24 Aug., 7 Oct., 18Nov. 1983.
Hahn, Peter; ibid., 13 Sept. 1983.
Bell, Robert; Architect, Harry Weese and Assoc.; Chicago, 111.; 9 Nov. 1983.
Winklestein, Peter; Partner, Marquis and Assoc., San Francisco, CA; 16 Nov. 1983.
Kreamer, Kofi; Associate Peace Director, Ghana; (in Denver); 3 Nov., 11 Nov. 1983.
AN AR.CH TULSIS ITE CTURAL
LI C D M AY 1 9 59-
DAVID C AISDEPSOM
(Ot Ji.atl WO 1 1 V A 3 1 3 X <5 v a
Tow T ^vovi w o I X V A T 3 li X 'll O W
1 r~< j ^|i=ii=ii=i| | i ii ii ii ii i l | |
TT^ -TT^r III r.-i-T- ?affP4-h----iLS''M
__ 5 E C T I O N A-A (scale i a q )
Through the analysis of this program it became apparent that a simple solution would be the most appropriate. At the outset the most important programmatic task was to keep the public and private functions of the program separate. The choice' to separate functions of the program spatially rather than vertically was deliberate. That choice came from a desire to keep the relative scale of the building low and to provide the private residence with a direct connection to the ground.
From the beginning, a sequence of events was sought that would serve as a series of transitions through the site. This was achieved by layering the forms and reinforced through the use of layers within those layers (ie. galleries and hallways). The layers are not intended to be separate from each other, therefore they were made transparent with some of the layers being defined by as little as a colonade. The transparency allows for a smooth transition from place to place as well as providing light and ventilation to the interior spaces.
The use of "roof architecture" came about as a response to both the climate and the cultural aesthetics. More than anything the concept of a roof rather than walls is
intended to convey a sense of "shelter" while steering away from the image of "fort." The hip roof is very common in Ghanaian architecture and allows for considerable ventilation in the upper reaches of the roof. Exaggerated overhangs maintain shade on all of the wall surfaces all day, thus reducing radiant solar gain.
As the design of the buildings progressed it became more and more apparent that color was going to play an important role in the overall effect of the buildings. In Ghana, buildings become the backdrop for the people. The color scheme for the building was therefore subtle with the basic hues taken from the natural colors of the woods that were being used inside. This necessarily created a pallette heavy on the yellow/ orange/red end of the spectrum. Blue was chosen as the accent.
The colors were intentionally chosen to avoid conflicts with the brilliant primary and secondary colors of Ghanaian fabrics. At the same token they would serve to enhance a purely black tie function as a very subdued background.
The landscaping was designed as a progression of layers with an emphasis on formality at the front entrance, fading into more random plantings elsewhere on the site. The one
exception to this is the relatively rigid plantation of the cocoa grove at the west end of the site. These trees create a canopy over the private drive and act as a filter for light and breezes.
In reality this is an academic problem. Only in a thesis situation could it be pursued with such freedom. This solution is set forth as a legitimate alternative to the design directions too often taken in our government buildings.
EMBASSY OF THE UNITED STATES OF AMERICA
November 10, 1983
Mr. David C. Anderson 420 W. 5th Avenue Denver, Colorado 80204
Dear Mr. Anderson:
Thank you very much for your letter of October 11, 1983, and your professional interest in designing a residence for U.S. Ambassadors. I'm sure you are concerned at the delay in response, but I'm sure you realize the difficulties in mail, even through the diplomatic pouch.
I regret that I cannot be of much detailed assistance to you. In contrast to whatever concerns Ambassador Robert Smith may have had, my wife and I find the Residence quite suitable for the smaller type functions we prefer and which are more in keeping with the current political situation in Ghana. That, by the way, is one of the problems of design -- every resident Ambassador and spouse have a different style and one person's essential is another one's opulence and vice-versa.
From a practical point of view, the essentials in my judgment include a pleasant representational but not opulent appearance, public rooms which lend themselves with a minimum of rearrangement to informal gatherings of various numbers, covered outside attractive areas, discreet but effective separation of private living quarters from the public areas, guest bedrooms again separate from the host's area, on-site quarters for staff, an efficient but
spacious kitchen servicing system, and, unfortunately in this day and age, a design which discreetly but effectively takes security concerns fully into account.
This latter concern probably explains why you have had some difficulty in receiving, building design and site plans. We are very chary these days of putting such items into the public domain.
Please give Ross Kreamer my best regards.
Concrete slabs decorate White House for security
WASHINGTON (AP) Three-foot-high concrete barriers were installed at two White House entrances Saturday, replacing sand-filled trucks that have blocked the gates since Thanksgiving against possible truck bombings like the one that killed 239 Americans in Beirut.
A White House official said the barriers, similar to the pre-cast concrete slabs often used to separate highway, lanes, were more aesthetically acceptable; than the dump trucks and would be permanent. \
The new barriers were arranged in a way that would prevent any would-be terrorist from crashing full-speed through the heavy wrought-iron gates that h^ve protected the entrances.
WITlljHE BARRIERS in place, anyone driving into the'White'House must slow down and turn sharply, to go through the gates.
The slabs, weighing tons, were placed outside gates leading to the driveway that circles around the White.-House South Lawrj,in,front of the presidential mansion and the Oval Office.
The same barriers also protects another nearby set of gates leading toa.driveway and parking-area between the White House and the Old Executive Office Building.
White House spokesman Marlin Fitzwater said the barriers did not represent an increase in security. Theyre just replacing the trucks with concrete barriers, he said.
A White House official, speaking on condition
he not be identified, said the change was made to produce a more aesthetically appropriate barrier. I think its fair to say its permanent.
The official said sand-laden trucks would still be used at other entrances. Trucks were stationed at a gate on the Pennsylvania Avenue side of the White House and on the west and cast sides of the compound. ,
SHEILA DIXON, a White House spokeswoman, said the installation of the concrete barriers began Friday night. Work continued on Saturday. At one point, a tuxedo-clad White House waiter brought a silver urrf of coffee out to the workmen.
The dump trucks were,-first parked at the White House gates on Thanksgiving Day in response to what officials had called possible bomb threats.
Jack Smith, a Secret Seryice spokesman, said the new barriers *are not positioned to completely shut off the gates hyt.were stationed to prevent a motorist-from Crashing through an entrance. A slow-moving vehicle still will have room to pass through the entrances, he said.
The day before White House security was tightened, police patrol cars and vans were parked outside the State Department to block several entrances, A department spokeswoman said the extra security was in response to possible bomb threats.
NOTES ON PAGE 177
WHO 6*440 0* 36N 00 10W
TEMPERATURE OEG C
TEAR JAN eeb mar APR MAY JUN JUL AUG SEP OCI NOV DEC
1941 27.* 28.2 28.* 28.3 27.2 26.7 23.3 2*. 1 26.1 26.6 27.3 27.8
1942 27.* 28.3 29.1 28.* 26.8 2*.7 2*.3 23.9 23.7 26.4 27.7 27.0
194J 26.8 27.3 27.* 27.* 26.3 2*.6 23.8 23.4 2*.6 2*.9 27.3 27.7
1944 27. J 27.7 27.3 28.* 27.7 26.2 23.3 24.4 23.3 27.0 27.9 28.3
194* 27.8 28.* 28.0 28.* 27.7 26.* 2*.8 24.6 23.3 26.4 27.8 27.*
1946 27.6 27.* 27.8 27.6 26.* 2*. 3 2*.8 23.9 23.2 2*.7 26.9 27.3
. 94 7 27.2 27.9 27.8 27.6 27.1 26.9 23.2 24.8 23.3 26.3 26. * 26.7
1948 26.7 27.3 28.1 27.3 26.3 2*. 3 2* .* 24.* 2*.9 26.4 26.7 27.6
1949 27.6 28.0 28.3 28.6 28.0 2*.6 2*.6 24.4 23.* 26.1 26.6 2 7.6
19*0 26.9 2 7.3 27.7 27.2 26.9 2*.4 2*. 3 23.6 2*.3 2*.6 26.* 27.1
MEAN 27.3 27.8 28.0 2 7.9 27.1 2*.9 2*. 7 24.3 23. 3 26.2 27.1 27.*
19*1 27.1 27.2 27.7 27.9 26.6 23.7 2*.9 2*.3 23.7 23.9 26.9 2 7.9
19*2 27.3 27.3 27.6 27.8 26.8 23.3 2*. 7 2*. 1 2*. 8 23.6 26.7 27.2
19*3 27.* 27.3 27.7 27.9 27.1 23.* 2*.3 23.8 23.3 26.1 26.9 27.2
19*4 26.7 27.2 27.3 27.0 26.7 23.2 23.6 2*.0 2*.9 23.* 26.6 27.3
19** 26.9 27.6 26.9 26.9 27.2 23.* 2*.* 2*.2 23.1 23.9 26. e 26.6
1 9*6 26.9 27.3 26.9 27.3 26.9 23.2 23.6 23.3 23.1 23.9 26.i 27.1
19*7 26.3 27.3 27.6 27.2 26.9 23.7 2*. 6 2*.7 23.* 23.8 27.3 27.6
19*8 27.8 28.1 28.2 27.7 26 2*.8 23.7 2*. 3 23.2 23.9 27.2 27.3
19*9 27.8 27.6 28.1 28.1 26.8 23.9 2*. 8 2*.3 23.3 26.6 27.3 27.*
1 960 27.6 27.9 28.0 27. 3 27.1 23.8 23.1 2*.9 26.0 26. 3 27.3 26.7
MEAN 27.2 27.3 27.6 27.3 26.9 23.3 2*.* 2*.3 23.3 23.9 27.0 27.2
CLINO 27.3 27.7 27.8 27.7 27.0 23.7 2*.6 2*. 3 23.3 26.1 27.1 27.3
YEAR JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
1941 6 40 4* ** 123 8* 111 1* 102 60 37 7
194 2 27 1 0 60 308 189 4 2 4 64 17 31
1943 1* ) 3 63 87 186 222 122 7 19 37 1 9 7
1944 6 27 71 16 238 367 197 6 30 91 6 3
194* 1* 27 83 33 7 66 14 28 23 92 9 20
1946 T 111 62 79 1 73 *1 1 1 3* 2* 24 9
1947 41 6 124 66 113 2 1 10 49 224 62 1 39 *6
1 948 0 39 12 61 170 167 * 7 2 *2 *3 17
1949 0 6 *1 14 ** 306 168 19 *1 63 *6 4
19*0 48 3* 113 1 10 1** 13i 67 3 2 9 44 T
MEAN 16.0 32.7 64.4 60.1 133.0 1*9.0 79.9 1 3.7 49.2 **.* * O 1 4
19*1 C T 97 19 297 1*6 19 26 6 160 10 32
19*2 17 *0 *7 33 200 3 2 90 128 22 7
19*3 6 114 36 44 176 89 *6 1* 26 172 32 29
19*4 29 *8 46 97 1 36 108 10 6 6 3 1 36 63 36
1 9** 6 21 1*4 203 77 7 30 1* 44 201 19 T
1 9*6 3 3 116 62 16* 1SS 28 * 31 6 7 44 32
1 9*7 T 3 108 104 1 66 1*1 7* 62 2 3 4* 9 1 9
1 9*8 9* 12 *2 132 166 87 1 l 29 6 3 49 2
1 9*9 T -.9 34 147 134 *)0 82 1 1 31 32 92 7
1 96U 4 4 30 108 7* 171 10 4 3 1 0 121 1 1 2 8
MÂ£ AN 16.0 31 .4 73.2 96.9 161.2 ;?e. 1 31 .4 16.8 37.* 116.7 3*. 1 19.4
CLINO 16 37 n 82 14* 191 49 1 6 4 C 80 38 1 8
27.1 2 6.7
26.3 26.6 26.1
26.4 26.0 26.2
26.4 2 6.7 26.7
26.4 26. *
l l 97
7*1 7** 709 1049 8 1 *
Ghana pavt iv 7s
ACCKA 5WN. SI ft.
Teaparature Relative humidity Precipitation
1 1188*1935 Average Average
Average of of Average of Average UaileaM. Ho. of
Bibliography dally highest lowest ADsolute obeervatlona aonthly fall In days with
72, 73, 76 each each at fall 24 hr. 001 in.
Mai. Min. aonth aonth Max. Min. 0600 1200 or BK>re
per aeat. JaeAes
January <7 73 91 67 94 59 95 61 0*6 3*5 1
February 8* 73 91 70 100 62 96 61 1*3 4*2 2
March 11 76 91 71 100 68 95 63 2*2 4-J 4
April 81 76 91 71 93 67 96 65 3*2 5*4 6
n*y 17 71 91 71 95 69 96 68 5*6 5*9 9
J> M 74 89 70 92 68 97 74 7*0 11*9 10
July 61 73 85 69 90 66 97 76 1*8 41 4
August 80 71 83 68 89 64 97 77 0*6 3*7 3
September 11 73 65 70 89 68 96 72 J-4 4*5 4
October 85 74 88 70 90 67 97 71 >3 5*5 6
Noveabar 87 75 89 71 91 69 97 66 1*4 3*7 3
December 86 75 90 69 94 63 97 64 0*9 3*0 2
Year 86 74 93* 65** 100 59 96 68 28*5 11-9 54
Ho. of yaara 17 17 17 17 17 17 9 9 65 64 46
TECHNICAL REPORT 660 7-05
PR0P03ED 3T1TT CPA3TER3 FCR AXERICiN PffljSST AT B0DVKI3EH 7IELD. CANTONMENTS ACCRA.
REPORT OF SITE INVESTIGATION
1 .0 IntroductIon :
1i1 The 3ite Investigation for the proposed American Embassy Staff
Quarters at the Budweiser field, Cantonments, Accra was requested by the General Services Officer of the American Embassy, Accra on behalf of Foreign Building Operations Department of State, Washington D.C.
1.2 The Architectural and Engineering Services Corporation was to evaluate the Subsoil Conditions at the site by drilling Eleven Bore Holes and suggest the type, depth of placement of foundation and other design criteria for the foundations of the proposed Buildings.
1.3 The proposed structures will be wooden framed Living Quarters like the ones already existing at the site.
2.0 Condition of the Existing Adjacent Buildings:
2.1 The Existing Adjacent Buildings for the Staff built several years back have not shown any sign of distress.
3.0 Topography Drainage and Vegetation;
3.1 The site is located in a fairly flat terran which has a gentle slope towards south. The vegetation is made up of grass, flowers, decorative trees and tushes.
4.0 field Work:
4.1 Eleven 3hell and Auger Bore Holes using 6" dia. casing were made.
4" dia. Selby tubes were used to extract undisturbed samples. The position
of bore holes as shown by the Client aj?e given in Drawing No. 660 F-1, attached with the Report. The depth of the test holes varied between 6.4 m. (21 ft.) and 7.6 m. (25 ft.) from the existing ground level depending upon the depth at which the hard rock was met.
4.2 The Drilling work was started during the first week of December 1982 and completed by the third week of January 1983.
4.3 Both undisturbed and disturbed samples from various depths were collected for testing^he Laboratory for Geotechnical Properties, Standard Penetration Tests were carried out at reguiar intervals in all the holes during drilling.
4.4 The Record for Subsurface Exploration showing type of soil encountered, type of sample taken, the depths at which samples were taken and the number of blows in Standard Penetration Teste are given in the Report. The number of blows in driving the 4" dia. x 18" long sampler is also appended.
5.0 Laboratory Testing!
5.1 Tha soil samples wars tasted for Index and Classification Tests
in accordance to procedures described in B.3. 1577 included natural moisture contents, Atterborgs Limits, Particle Size Distribution and Density Tests.
To determine Engineering Properties, Consolidation and Shear Strength Teats were carried out on selected undisturbed samples. The results are given in SUmmary of Test Results attached with the Report.
6.1 The Site Exploration reveals that the site is underlain by the Dahomayan gneiss which is the bedrock at the area. Overlying the parent bedrock is the hard weathered Biotitic gneiss. The degree of weAthering decreases with depth. The upper layers of weathered gneiss are practically structureless tut the gneissic structure becomes clearly visible as depth increases. This layer is in turn overlain by a mixture of residual soil of stiff mottled sandy clay and silty sand which grades into a laterised gravelly soil. The soil profile showing depth of various soil layers is given in Drawing No. 660 F-2.
7.0 Ground Water Condition:
7.1 The water was encountered in BH-11 at the depth of 2.74-3 m. (9 ft.) during drilling and went down to 3.099 m. (10 ft. 2 in.) the following day
3 hours after removal of casing. In BH-9, the ground water showed up at depth of 6.884 a. (22 ft. 7 in.) few days after the completion of boring and removal of casing. In other bore holes no water was encountered. Seepage of water in BH-11 is likely to have occured from some leaking drainage and water supply installations.
7.2 The Chemical Analysis of the ground water of BH-9 and BH-11 shows sulphate as So^ 225 parts per million and PH equal to 7 and 8 for BH-9 and II respectively.
8.0 Geotechnical Properties:
8.1 Classification The natural moisture contents of the samples are quite low ranging between-55 $ to 16.8 $. This may be due to the high sand content and presence of gravel. The liquid limits vary between 18 79$ while the plastic limits vary between 13 42 $. The Plasticity Index varies between 3-39 indicating that the material is of low to medium plasticity.
The particle size distribution results indicate that the materials at site are mainly sand, sandy loams and silty clay.
8.2 Shear and Consolidation Characteristics: The triaxial shear tests, (quick undrained) showed high angle of internal friction for sandy soils and value of cohesion for clayey soils. One dimensional consolidation tests were carried out on some selected samples. The values of void ratios for various pressures are given in the Summary of Test Results. By comparing the consolidation pressures at various depths with overburden pressure it has been noted that the soils have been over consolidated.
8.3 Standard Penetration Teetsi These registered vary high values for
tha weathered biotitic gneiss ranging fro* 33 to refusal indicating that the material la dense to very danse. The material overlying the weathered gneiss recorded values from 9 blova/ft. to refusal which also indicates loose to very dense. The standard penetration test values have been recorded in the Bore Hole profile in Drawing Ho. 660 F-2. Those results of S.P.T. in which the penetration could not take place for full 12 inch due to hardness have
been shown as> 50 in the profile plot. Infact these can be taken as state
of refusal. In some cases, swelling pressures up to 4" to 1 kg/cm were observed.
9.0 Depth of Foundations:
9.1 In Bore Holes 1 and 2 the material upto 2 m. depth is soft with S.P.T of 9 blows per foot. The values of C and / for BH-2 at depth of 1.5
to 2 m. was determined as 5.3 pai and 8. But after 2 m. depth the formation becomes harder and at 2.5 m. depth the S.P.T. value is 18 in 3H-1 and 24 in BH-2. The depth of 2 m. is considered suitable for foundingj^the blocks 1 and B (part). However, considering the type of structures, it may not be economical to take the footings to such depth. It is suggested that in portions where the soft material is encountered during digging, the same may be removed and replaced by a gravelly lateritic soil or any other granular non plastic material and compacted up to 1.2 m. depth (4 ft.) before putting the footings. In all other Bore Holes the formation from 1 m. depth is quite compact and the footings can be placed at 1.2 m. depth.
10.0 Allowable Bearing Capacity:
10.1 After replacing the soft patches in area covered by BH-1 and BH-2 by compacted granular material,-the foundations can be placed at depths of
1.2 m. (4 ft.) with allowable bearing capacity of 2 kg/cm for square footings upto 1.5 m. side.
10.2 At depth of 1.2 m. and with contact pressure of 2 kg/cm the maximum settlement (sum of consolidation and Immediate settlement) for 1.2 m. square footings works out 4.5 cm. (l1 8 in.). For the type of structures envisaged this settlement is considered not excessive. As details of structures i.e. loads etc. are not available, differential settlement cannot be worked out.
11.1 The site is underlain by Dahomeyan gneiss. No- faults are believed to exist at the site. Excepting in BH-1 and BH-2 the material at 1 m. depth and below is quite compact and fit for founding the structure.
11.2 Where the material at 1.2 m. depth is soft as in BH-1 and BH-2
the same may be removed from the foundation pits up to about 2 m. depth and the pits filled back upto 1.2 m. depth with suitable granular material and compacted. All footings can be placed at depth of 1.2 m. from the existing ground level.
11.3 An allowable bearing capacity of 2 kg/cm can be taken for
proportioning the footings.
11.4- A settlement ofAJj cm is expected which ia not considered
excessive. Aa the material is mostly sandy the major portion of settlement would have taken place during construction.
11.5 Swell pressures upto about 1 kg/cm have been observed during
consolidation tests. It is recommended that good drainage is provided around the buildings.